Caroline Wozniacki will end season as number one

Caroline Wozniacki will end the tennis season as world number one following Maria Sharapova's withdrawal from the WTA Championships in Istanbul.

World number two Sharapova was forced to retire from the competition this evening with an ankle injury.

As a result 21-year-old Wozniacki can no longer be caught at the top of the rankings, having amassed 7395 points over the last 12 months.

Sharapova, who is the Dane's closest challenger, will end the year with 6370 points.